This invention relates to a weft guide device in a jet loom.
Heretofore, in order to allow a weft to be smoothly inserted through the warp shed of a jet loom by flow of air discharged from a main nozzle arranged in a known manner, a weft guide device has been provided which comprises a number of weft guide members arranged near the reed in line with each other in the weft insertion direction, the weft guide members each being provided, for example on the side of the reed, with interiorly facing surfaces providing either a large weft guide opening (hereinafter referred to as the open type) or a small weft guide opening (hereinafter referred to as the closed type) sufficiently narrow to just allow the escapement of the weft therethrough, these surfaces being in alignment with each other to provide a weft guide path, and a suitable number of air discharge sub-nozzles arranged in predetermined locations along the weft guide path so that air outlets formed therein face the weft guide path. In this weft guide device, each of the sub-nozzles discharges a jet of air assisting the air jet from the main nozzle in carrying out the weft insertion; otherwise the leading end of the weft will not be able to be moved far enough during the weft inserting operation.
However, the weft guide device employing the open type weft guide members encounters the problems that because of the large openings provided by the respective weft guide surfaces of the guide members, the air discharged from the main and sub-nozzles is apt to easily escape through the large openings, resulting in a larger air consumption; and that during the weft inserting operation, the leading end of the weft may be entrained in the air currents escaping through the openings and erroneously moved out of the weft guide path.
In the weft guide device employing the closed type guide members, the weft insertion can not rely on the main nozzle alone when inserting through a relatively long weft guide path. Thus, some of the weft guide members arranged in the predetermined positions are formed into a hollow structure with an air passage therein and air outlet or outlets facing the weft guide path so that the pressurized air supplied to the air passage is discharged through the outlet or outlets into the weft guide path. However, since these hollow members require that the air passage and outlet(s) be formed therein while maintaining them in a shape similar to the remaining weft guide members, it is difficult to conform the size or dimensions of the hollow members to the remaining weft guide members. For example, the small opening, provided in the concave of each hollow member to allow the weft to escape from the weft guide path after the weft insertion, becomes inconsistent in position with the small openings in the remaining weft guide members. This may result in the failure of the weft insertion. Furthermore, it is difficult to ensure that the air outlet is so opened that the air flow therethrough is directed in the predetermined direction allowing the air flow to attain its object of assisting the main nozzle. This results in a critical disadvantage directly affecting the weft inserting function of the guide device. Thus, it is understood that the guide device employing the closed type guide members requires highly advanced manufacturing technology.
For these reasons, Japanese laid-open patent specification No. 55-128,047 has proposed a combined weft guide device including, as shown in FIGS. 1(A) and 1(B) hereof, both open type guide members 2 each having a concave shaped interior surface 1 with a large opening 5 on the left-hand side thereof, and closed type guide members 4 each having an interior surface 3 providing a small opening 6, in order to positively utilize the advantages of the open and closed type guide members. In this combined device, guide members 2 (FIG. 1(B)) are deliberately scattered throughout the array of guide members 4 (FIG. 1(A)) with their respective concaved surfaces 1 and 3 arranged in line. The weft escape openings 5 and 6 are formed on the side of a reed 12 as can be seen in FIG. 2. In front of the escape opening 5 of each guide member 2, a vertical sub-nozzle 19 (FIG. 2) is arranged to provide an auxiliary flow of air, and the weft escape opening 6 is provided on the side of the reed and in the upper part of concaved surface 3 between first and second arms 7 and 8 of weft guide member 4.
This combined guide device can prevent to some degree a great loss of discharged air accompanied by a weft insertion error. Also, this combined guide device does not require that an air passage be formed in any of the weft guide members and therefore can eliminate the difficulty in manufacturing the weft guide members.
However, in the combined guide device described above, as shown in FIG. 1(A), the second arm 8 of guide member 4 has an inner wall surface 3d (defining the rear wall of the surface 3) extending substantially straight upward to define opening 6. The substantially straight surface 3d can not cause the air discharged into the weft guide path to be effectively and satisfactorily converged during the weft inserting operation. Therefore, the air flow in the weft guide path is apt to branch away to the weft escape openings 5 and 6. This causes not only an increased air consumption, but also an unexpected movement of the weft through the openings out of the weft guide path entrained in the branch air flow, resulting in the failure of the weft insertion. In other words, the air flow discharged from the sub-nozzle is blown against the fore wall surface 3a of the concaved surface 3 and thereafter a portion thereof flows along the lower wall surface 3c toward the rear of the jet loom (the side of the second arm 8) and then upwardly along the rear wall surface 3d toward opening 6. Thus, said portion of the air flow is discharged out of the weft guide path through opening 6 and causes the failure of the weft insertion.
Accordingly, it is a primary object of this invention to provide a weft guide device for a jet loom, which, in order to eliminate the disadvantages of the prior art, can effectively use main and auxiliary air flows to decrease power consumption, allows easy manufacture of weft guide members, and enables a weft to pass through a weft guide path in a stable state to increase the speed of a weft insertion and cause the leading end of the weft to travel a longer distance, resulting in increased width in high speed jet looms.